C

    Paul is a photographer(摄影师). He went to the Arctic to take pictures for NationalGeographic(《国家地理》). Finally, he saw a big and white polar bear swimming to him in the icy water.

    Paul lay down the ice to get a better photo, but the polar bear jumped out of the water and tried to attack him! Luckily for Paul, the ice cracked(破裂), or broke and the bear fell back into the water. The polar bear wasn't so lucky. It couldn't get a meal and had to swim farther away to find food.

    To understand the polar bear's problem, you need to know two things about the Arctic. First, the Arctic is mostly ocean(海洋). Second, ice covers(覆盖) a lot of the Arctic Ocean. In winter, the ice is thick, but in summer, the ice becomes thinner and breaks into pieces. Sea ice is the key to survival for Arctic animals. However, because of global warming, Arctic temperatures are rising and polar ice is melting(融化).

    Polar bears need ice  to hunt(捕捉) seals, their favourite meal. They stand on the ice and wait for the seals to come up for air. As Arctic ice melts, polar bears have to swim farther to find ice floes, or large pieces of floating ice. Sometimes, bears have to swim more than 200 km to find an ice floe. Some bears cannot swim that far and sadly they drown(淹死).

    On his last trip, Paul saw three dead bodies of polar bears. Before global warming threatened(威胁) Arctic ice, a dead bear was a rare sight. Paul is sad to see the dead bodies. Wildlife experts(专家) think global warming will have a terrible effect(影响) on polar bears. In the future, polar ice will continue to shrink and endanger the bears. Some scientists believe 65 percent of the world's polar bears will disappear(消失) by 2050. In other words, polar bears are in great danger.

D

    It is reported that some developed countries have shipped broken parts of computers to China. Last month Hong Kong officers found 131,000 kilograms of broken computers, TVs and phones sent from Japan.

    Things like these are called electronic waste, or e-waste. Dealing with them is not an easy job. Every time an old computer breaks down, it needs to be dealt with safely. What is worse, at present, broken computer parts are usually buried. It may be hundreds of years before they are really g one in the earth.

    Many places in China are polluted by e-waste. Guiyu in Guangdong Province is one of them. This town is named as "the e-waste capital of the world". It has to deal with 1.5 million kilograms of e-waste each year, from which it makes 75 million yuan. But it comes at a cost. Many of the poisons in e-waste find their way into the environment. An environmental group has found the air, the earth and the rivers in Guiyu badly polluted.

    Luckily, the Chinese government wants to change the situation. This year, China passed a new environmental protection law. Computer companies like Lenovo and Dell will be asked to take back their old computers. Hopefully, the problem with e-waste will be solved in the near future.

    China Science and Technology Museum was opened to the public in September 1988. But the second project was completed in May, 2000. Its main task is to spread knowledge of science and technology among the public.

    The activities of China Science and Technology Museum include popular science exhibitions, Astro­vision film shows, training education programmes and experiment exhibition programmes. The museum has an area of 40，000 square metres, of which 16, 000 square metres is for exhibition halls.

    The Astro­vision Theatre is one of the museum's major attractions and also one of the largest Astro­vision theatres in the world. It makes visitors feel they are in actual events rather than see a film. Many great science activities are often held at the museum, and the museum wants to be an important window to the world.

    The word, "photography", was first used in 1839. It comes from the Greek words that mean "to write with light". But photography could only give people static pictures. So scientists were trying hard to find ways to make pictures that can move. They made lots of experiments, but failed again and again. It was Eadweard Muybridge who finally succeeded. He was the first photographer to try this successfully. But how did he make it? It was an interesting story.

    Back in 1872, people didn't know exactly(确切地) whether all four of a horse's hooves(蹄) left the ground at the same time when it was running. A gentleman called Leland Stanford made a bet with his friend about it. Most people believed that a horse always had one hoof on the ground, or it would fall over. But Stanford didn't think so.

    At that time, it was hard to know who could win the bet, because a horse's legs move so fast that it is impossible to tell just by looking. So they needed a way to record the movement of a running horse. Then Stanford offered $ 25,000 to the famous photographer, Muybridge, to help find the answer. In the beginning, Muybridge failed to get clear images, but he didn't give up. He continued to improve his cameras. In 1878, after many experiments, he managed to get a sequence(连续) of 12 photos. One of them clearly showed that all four of the horse's hooves were off the ground at the same time. And when the photos moved fast, people could see a horse running.

    Though Edison is usually considered as the person who created the first movie in 1889, it was the work of Eadweard Muybridge and the bet that led to Edison's invention.